A zinc oxide (ZnO) nanoparticle photodetector was fabricated using a simple method. Under a 5 V applied bias, its dark current and photocurrent were 1.98 × 10−8 and 9.42 × 10−7 A, respectively. In other words, a photocurrent‐to‐dark‐current contrast ratio of 48 was obtained. Under incident light at a wavelength of 375 nm and a 5 V applied bias, the detector’s measured responsivity was 3.75 A/W. The transient time constants measured during the turn‐ON and turn‐OFF states were τON = 204 s and τOFF = 486 s, respectively.